/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.springframework.boot.logging.log4j2;

import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Marker;
import org.apache.logging.log4j.core.Filter;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.Logger;
import org.apache.logging.log4j.core.LoggerContext;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.ConfigurationFactory;
import org.apache.logging.log4j.core.config.ConfigurationSource;
import org.apache.logging.log4j.core.config.LoggerConfig;
import org.apache.logging.log4j.core.filter.AbstractFilter;
import org.apache.logging.log4j.message.Message;
import org.springframework.boot.logging.LogFile;
import org.springframework.boot.logging.LogLevel;
import org.springframework.boot.logging.LoggerConfiguration;
import org.springframework.boot.logging.LoggingInitializationContext;
import org.springframework.boot.logging.LoggingSystem;
import org.springframework.boot.logging.Slf4JLoggingSystem;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.ResourceUtils;
import org.springframework.util.StringUtils;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Set;

/**
 * {@link LoggingSystem} for <a href="https://logging.apache.org/log4j/2.x/">Log4j 2</a>.
 *
 * @author Daniel Fullarton
 * @author Andy Wilkinson
 * @author Alexander Heusingfeld
 * @author Ben Hale
 * @since 1.2.0
 */
public class Log4J2LoggingSystem extends Slf4JLoggingSystem {

    private static final String           FILE_PROTOCOL = "file";

    private static final LogLevels<Level> LEVELS        = new LogLevels<>();

    static {
        LEVELS.map(LogLevel.TRACE, Level.TRACE);
        LEVELS.map(LogLevel.DEBUG, Level.DEBUG);
        LEVELS.map(LogLevel.INFO, Level.INFO);
        LEVELS.map(LogLevel.WARN, Level.WARN);
        LEVELS.map(LogLevel.ERROR, Level.ERROR);
        LEVELS.map(LogLevel.FATAL, Level.FATAL);
        LEVELS.map(LogLevel.OFF, Level.OFF);
    }

    private static final Filter FILTER = new AbstractFilter() {

        @Override
        public Result filter(LogEvent event) {
            return Result.DENY;
        }

        @Override
        public Result filter(Logger logger, Level level, Marker marker, Message msg, Throwable t) {
            return Result.DENY;
        }

        @Override
        public Result filter(Logger logger, Level level, Marker marker, Object msg, Throwable t) {
            return Result.DENY;
        }

        @Override
        public Result filter(Logger logger, Level level, Marker marker, String msg,
                             Object... params) {
            return Result.DENY;
        }

    };

    public Log4J2LoggingSystem(ClassLoader classLoader) {
        super(classLoader);
    }

    @Override
    protected String[] getStandardConfigLocations() {
        return getCurrentlySupportedConfigLocations();
    }

    private String[] getCurrentlySupportedConfigLocations() {
        List<String> supportedConfigLocations = new ArrayList<>();
        supportedConfigLocations.add("log4j2.properties");
        if (isClassAvailable("com.fasterxml.jackson.dataformat.yaml.YAMLParser")) {
            Collections.addAll(supportedConfigLocations, "log4j2.yaml", "log4j2.yml");
        }
        if (isClassAvailable("com.fasterxml.jackson.databind.ObjectMapper")) {
            Collections.addAll(supportedConfigLocations, "log4j2.json", "log4j2.jsn");
        }
        supportedConfigLocations.add("log4j2.xml");
        return StringUtils.toStringArray(supportedConfigLocations);
    }

    protected boolean isClassAvailable(String className) {
        return ClassUtils.isPresent(className, getClassLoader());
    }

    @Override
    public void beforeInitialize() {
        LoggerContext loggerContext = getLoggerContext();
        if (isAlreadyInitialized(loggerContext)) {
            return;
        }
        super.beforeInitialize();
        loggerContext.getConfiguration().addFilter(FILTER);
    }

    @Override
    public void initialize(LoggingInitializationContext initializationContext,
                           String configLocation, LogFile logFile) {
        LoggerContext loggerContext = getLoggerContext();
        if (isAlreadyInitialized(loggerContext)) {
            return;
        }
        loggerContext.getConfiguration().removeFilter(FILTER);
        super.initialize(initializationContext, configLocation, logFile);
        markAsInitialized(loggerContext);
    }

    @Override
    protected void loadDefaults(LoggingInitializationContext initializationContext,
                                LogFile logFile) {
        if (logFile != null) {
            loadConfiguration(getPackagedConfigFile("log4j2-file.xml"), logFile);
        } else {
            loadConfiguration(getPackagedConfigFile("log4j2.xml"), logFile);
        }
    }

    @Override
    protected void loadConfiguration(LoggingInitializationContext initializationContext,
                                     String location, LogFile logFile) {
        super.loadConfiguration(initializationContext, location, logFile);
        loadConfiguration(location, logFile);
    }

    protected void loadConfiguration(String location, LogFile logFile) {
        Assert.notNull(location, "Location must not be null");
        try {
            LoggerContext ctx = getLoggerContext();
            URL url = ResourceUtils.getURL(location);
            ConfigurationSource source = getConfigurationSource(url);
            ctx.start(ConfigurationFactory.getInstance().getConfiguration(ctx, source));
        } catch (Exception ex) {
            throw new IllegalStateException("Could not initialize Log4J2 logging from " + location,
                ex);
        }
    }

    private ConfigurationSource getConfigurationSource(URL url) throws IOException {
        InputStream stream = url.openStream();
        if (FILE_PROTOCOL.equals(url.getProtocol())) {
            return new ConfigurationSource(stream, ResourceUtils.getFile(url));
        }
        return new ConfigurationSource(stream, url);
    }

    @Override
    protected void reinitialize(LoggingInitializationContext initializationContext) {
        getLoggerContext().reconfigure();
    }

    @Override
    public Set<LogLevel> getSupportedLogLevels() {
        return LEVELS.getSupported();
    }

    @Override
    public void setLogLevel(String loggerName, LogLevel logLevel) {
        Level level = LEVELS.convertSystemToNative(logLevel);
        LoggerConfig loggerConfig = getLoggerConfig(loggerName);
        if (loggerConfig == null) {
            loggerConfig = new LoggerConfig(loggerName, level, true);
            getLoggerContext().getConfiguration().addLogger(loggerName, loggerConfig);
        } else {
            loggerConfig.setLevel(level);
        }
        getLoggerContext().updateLoggers();
    }

    @Override
    public List<LoggerConfiguration> getLoggerConfigurations() {
        List<LoggerConfiguration> result = new ArrayList<>();
        Configuration configuration = getLoggerContext().getConfiguration();
        for (LoggerConfig loggerConfig : configuration.getLoggers().values()) {
            result.add(convertLoggerConfiguration(loggerConfig));
        }
        result.sort(CONFIGURATION_COMPARATOR);
        return result;
    }

    @Override
    public LoggerConfiguration getLoggerConfiguration(String loggerName) {
        return convertLoggerConfiguration(getLoggerConfig(loggerName));
    }

    private LoggerConfiguration convertLoggerConfiguration(LoggerConfig loggerConfig) {
        if (loggerConfig == null) {
            return null;
        }
        LogLevel level = LEVELS.convertNativeToSystem(loggerConfig.getLevel());
        String name = loggerConfig.getName();
        if (!StringUtils.hasLength(name) || LogManager.ROOT_LOGGER_NAME.equals(name)) {
            name = ROOT_LOGGER_NAME;
        }
        return new LoggerConfiguration(name, level, level);
    }

    @Override
    public Runnable getShutdownHandler() {
        return new ShutdownHandler();
    }

    @Override
    public void cleanUp() {
        super.cleanUp();
        LoggerContext loggerContext = getLoggerContext();
        markAsUninitialized(loggerContext);
        loggerContext.getConfiguration().removeFilter(FILTER);
    }

    private LoggerConfig getLoggerConfig(String name) {
        if (!StringUtils.hasLength(name) || ROOT_LOGGER_NAME.equals(name)) {
            name = LogManager.ROOT_LOGGER_NAME;
        }
        return getLoggerContext().getConfiguration().getLoggers().get(name);
    }

    private LoggerContext getLoggerContext() {
        return (LoggerContext) LogManager.getContext(Thread.currentThread().getContextClassLoader(),
            false);
    }

    private boolean isAlreadyInitialized(LoggerContext loggerContext) {
        return LoggingSystem.class.getName().equals(loggerContext.getExternalContext());
    }

    private void markAsInitialized(LoggerContext loggerContext) {
        loggerContext.setExternalContext(LoggingSystem.class.getName());
    }

    private void markAsUninitialized(LoggerContext loggerContext) {
        loggerContext.setExternalContext(null);
    }

    private final class ShutdownHandler implements Runnable {

        @Override
        public void run() {
            getLoggerContext().stop();
        }

    }
}
